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Sent: Friday, August 22, 1997 3:22 AM
To: 'Dinosaur Mailing List - Gen. Distribution'
Subject: Re: Dinosaur Weights
R. McNeill Alexander's book - "Dynamics of Dinosaurs & Other Extinct Giants" -
Columbia University Press [New York] 1989. Pages 16 to 26 - 'Weighing
Dinosaurs'
In that chapter, you'll see how the displacement experiment is done (look at
the diagram - and read the text - the dino model is suspended in a beaker
[dry], with a weight attached to it, and it balances a group of weights on the
other side of a scale [balance beam]. Once that equilibrium is reached, then
you add the water until the entire model is under water. The amount of
weights that you have to remove to return it to equilibrium is the
displacement.), and that "Most animals have about the same density as water."
This is about 1000 kilograms per cubic meter.
On a test he did with a model of Brachiosaurus - the model displaced 728 grams
of water - which equals 728 cubic centimeters of displacement. The model was
1:40 scale. To scale the volume up you must multiple by 40 by 40 by 40, or
64,000!!! (64,000 x 728 = 46,600,000 cubic centimeters or 46.6 cubic meters).
46.6 cubic meters x (1000 kilograms/cubic meter) = 46,600 kilograms [or as
he puts it - 46.6 tonnes]. That's 102520 pounds for the metrically impaired
or about 51 US tons.
As R. McNeill explains, a lot depends on the dinosaur model you have. The
closer to actual shape the better the estimate.
By the way - Weight equals Mass times the Acceleration due to gravity. On
this planet, we are accustomed to describing something by its weight or mass
as though they were equal - they are related by a constant (32 feet per
second per second OR 9.8 meters per second per second). Mass is an
intrinsic property of an object - it stays the same no matter where the object
is. Weight varies depending upon the gravitational pull. 'Weightlessness'
(actually properly called 'microgravity' is when our apparent weight
approaches zero - due to the balance of gravitational pulls of the Earth and
the Moon and the acceleration of the vehicle. Our mass remains the same
(unless we vomit due to the queasy feeling). [Note that this is actually a
simplistic definition of microgravity - Mickey chastised me severely for not
including all the details].
:)
[By the way - this was reposted by me - due to some errors between my ISP and
the dinolist -- A.]